Apparatus for completing wells



Dec. 6, 1955 o. J. M CULLOUGH APPARATUS FOR COMPLETING WELLS 2 Sheets-Sheec 1 Filed Jan. 5, 1952 U hm m 9m 0 WW w M A c W w 0 Dec. 6, 1955 o. J. M CULLOUGH APPARATUS FOR COMPLETING WELLS 2 Sheets-Sheet 2 Filed Jan. 5, 1952 O L/. M Cu//0ug/z INVENTOR.

ATTORNEY United States Patent APPARATUS FOR CQMPLETING WELLS Otis Johnson McCullough, Houston, Tex., assignor of one-half to Ira J. McCuilough, Los Angeles, Calif.

Application January 5, H52, Serial No. 265,095

4 Claims. (Cl. 166-224) This invention relates to methods and apparatus for completing wells such as oil or gas wells.

In the drilling of wells for the production of oil or gas, a conventional procedure is to drill through the prospective producing formation and to then run a string of metallic casing or a liner into the bore hole and through the formation. The casing or liner is then cemented in the conventional manner to seal-off the prospective producing formation from underlying or overlying Watercontaining formations, or from both. Thereafter, the metal casing or liner is perforated by means of bullets or shaped explosive charges which are designed to pierce the pipe and surrounding cement sheath and to penetrate into the surrounding earth formations to thereby provide channels through which the fluids, such as oil or gas, in the formation may discharge into the casing or liner whence the fluids may be conducted to the surface by any of the usual methods.

While such methods of completion have proven very successful, it is recognized that one of their principal disadvantages resides in the fact that the total area of the drainage channels thus provided is necessarily quite small in relation to the total area of the formation exposed to the bore hole, since such channels will usually consist of only a relatively few small holes per lineal foot of formation. In general practice about four holes per foot will be shot. These holes will rarely, if ever, exceed one-half inch in diameter at the inner wall of the casing and will usually taper off to about half that diameter in the formation. Four one-half inch holes in a one-foot length of the Wall of a well bore, say seven inches in diameter, a common size, will correspond to about three-tenths of one percent of the total area represented by a foot of the formation exposed to the well bore. Thus even a ten-fold increase in the number of such perforations per foot of formation, a generally impractical possibility, would provide a channel area corresponding to only about three percent of each foot of formation to drain the formation into the interior of the metal casing or liner. Moreover, the very small diameter of the individual perforations makes them very easily subject to becoming plugged by sand, formation particles, or other detritus, thereby further reducing the area of the drainage channels to the casing, a condition very commonly encountered in practice.

It becomes highly desirable, therefore, to effect completion of a well in such a manner that a maximum area of the formation face may be placed in drainage communication with the Well casing.

The present invention is directed to a method and apparatus by which this highly desirable result may be attained in a simple and highly effective manner.

In accordance with one embodiment of this invention, this desirable result may be obtained by running into the well a conventional metal pipe string, such as casing or a liner, which has installed therein a section of strong glass tubing which, when the casing is set, will be positioned opposite, and surrounded by, the producing for- ICC mation. This casing including the glass section may then be cemented in place in the conventional manner, the glass section functioning in all respects as an integral part of the metal casing. Thereafter the glass section is broken out in any suitable manner, as by setting off a charge of high explosive in the bore of the glass section so that the resulting explosion will shatter the glass section and cement sheath between the glass section and the formation face, thereby exposing the entire surface of the latter to the bore of the casing. In any event, the glass section may be thus shattered and, if necessary, the surrounding cement and the adjacent face of the formation removed or cleaned out by suitable and conventional means and methods through the large opening thus'provided in the wall of the pipe string.

In accordance with another embodiment of this invention, instead of employing the continuous glass section described above, a section of metal casing may be employed which is provided with a plurality of relatively large glass windows which, when shattered by the explosion will provide a corresponding plurality of relatively large openings in the metal casing for access to the surrounding casing.

Additional embodiments and various other objects and advantages of this invention will become apparent from the following detailed description when read in conjunction with the accompanying drawings which illustrate several useful embodiments in accordance with this invention.

In the drawings:

Fig. 1 is a longitudinal view, partly in section, of a pipe string constructed in accordance with one embodiment of this invention to include a glass walled section, shown in position in a well bore opposite a producing formation preparatory to shattering the glass walled section;

Fig. 2 is a view similar to Fig. 1 after the glass walled section has been opened to the producing formation;

Fig. 3 is a longitudinal sectional view of a pipe string in accordance with another embodiment of this invention;

Fig. 4 is a cross-sectional view along line 4-4 of Fig. 3;

Fig. 5 is a longitudinal sectional view of one form of connector element for connecting the glass section of the V pipe string to an adjacent metal section; and

Fig. 6 is an elevational view showing another embodiment of this invention in position in a well bore.

Referring first to Fig. 1, there is shown a well bore 10 which has been drilled by generally conventional means and methods through an earth formation 11 which contains fluid, such as oil or gas, which is sought to be produced. Formation 11 is shown as positioned between overlying and underlying earth formations 12 and 13, re spectively, one or both of which may contain undesired connate fluids such as water. The apparatus for completing the well for production includes a pipe string, designated generally by the numeral 14, which is somewhat smaller in diameter than well bore 10 and which is inserted into the well bore from the surface and extends therefrom through earth formation 11 in accordance with conventional practice.

Pipe string 14 is composed of a plurality of sections 15-15 of conventional metal pipe provided with thread ed collars 16-16 for connecting the sections in end-toend relation. Between two of the metal pipe sections and forming a part of the pipe string, there is interposed a section 17 constructed of strong walled glass tubing having a length which may correspond to that of earth formation 11, or to a substantial portion thereof. Glass pipe section 17 is connected to the adjacent metal pipe sections 15-15 by means of collars 16-16. Al-' though glass tubing is commercially available which has sufficient tensile and radial strength to meet the requirements of this invention, its inherent brittleness makes it impractical to attempt to connect the ends of section 17 directly to the metal composing collars 16. Fig. 1 illustrates one form of connection between one end of section 17 and an adjacent metal pipe section by which this difficulty may be overcome, it being understood that the opposite end of section 17 will have a similar connection to the other metal pipe section adjacent thereto. As shown in Fig. l, collar 16 has one end threadedly connected to the end of metal pipe section in the conventional manner. The opposite end of collar 16 is provided with an internally threaded socket 18 adapted to receive the end of glass section 17 which is externally threaded at 19. The internal diameter of socket 18 is made appreciably greater than the external diameter of the threaded end of section 17 to thereby provide an appreciable annular space between them for the reception of a connector sleeve or bushing which is composed of resilient composition material, such as natural or synthetic rubber, and which is provided with internal and external threads for engagement, respectively, with threads 19 and those in socket 18.

The resilient connection thus formed by bushing 20 between the glass and adjacent metal parts will protect the glass from direct contact with metal, will absorb shock between them and will also provide a degree of flexibility in the joints between the glass section and the adjacent metal sections which will absorb to a substantial degree any bending stress to which the glass section may be subjected when the pipe string is being run into the well bore.

The abovedescribed apparatus may .be employed as follows to perform the method in accordance with this invention: Pipe string 14, having glass section 17 installed therein, will be lowered into well bore 10 to position glass section 17 opposite earth formation 11. Pipe string 14 may then be cemented in place by employing entirely conventional cementing procedures, the details of which form no part of the present invention. As is well understood by those skilled in this art, a cement slurry will be pumped-into the bore of pipe string 14 at the surface and will be displaced downwardly therethrough by means of a suitable displacing fluid, which will force the cement out of suitable openings in the pipe string at some -point along formation 13, well below formation 11, and thence up through the annular space between the pipe string and the wall of well bore 10 to some previously determined level in formation 12 which will usually be well above the top of formation '11. When the cement, indicated at 21, hardens it will form a seal between the pipe string and the well here to thereby seal-off formation 11 from the overand under-lying earth formations.

When pipe string 14 has been cemented in place, as described, glass section 17 may be shattered by means of a suitable shattering device which may be run through the bore of the pipe string to a point adjacent glass section 17. The cement sheath lying between section 17 and earth formation 11 may then be removed through opening thus formed in the wall of the pipe string thereby exposing substantially the entire surface of formation 11 for communication and drainage through the relatively large opening thus formed in the wall of the pipe string.

While various devices may be employed for shattering section 17, i prefer to effect this operation by means of an explosive charge which is inserted in the bore of section 17 and set off therein. As illustrated in Fig. 1, this operation may be performed by employingan explosive charge 22 of narrow elongated form, having a'length such as to extend throughout the major portion of the length of section 17. Such an explosive charge may consist of a piece of conventional explosive detonating cord, such as the well-.known Primacord, which, generally speakingiscomposed of a hollowfa'oric opplastic tube, the bore of which is filled with one of the known high explosives, such as pentaerythritoltetranitrate. The piece of explosive cord 22 .will be connected to an electrical firing head 23 of any well-known and suitable design which will, in turn, be suspended from a cable 24, of conventional form, which will be employed to lower the explosive charge through the pipe string and to conduct electric current to the firing head.

When explosive charge 22 has been positioned in the bore of section 17 and is set off, the resulting explosion will completely shatter the glass walls of section 17 and thereby provide an opening in the wall of the pipe string which, in the illustrative example, will extend throughout the length of earth formation 11. Ordinarily, the force of the explosion will be suflicient to shatter the cement sheath intervening between section 17 and earth formation 11 to such an extent that the cement will not seriousiy hinder the fiow of fluid, such as oil or gas, from formation 11 into the large opening thus formed in the pipe string. If found desirable or necessary, suitable tools, such as a conventional expansible wall scraper or under-reamer well known in the oil industry, may be run through "the pipe string and operated through the opening formed by the shattering of section 17 to remove any portion of-the cement which remains in place.

By the described operation, it will be evident that substantially the entire area of formation 11 traversed by the well bore will be opened to communication with the bore of the pipe string thereby permitting maximum flow of production fluid from the formation into the pipe string. Atthe same time, the metal pipe sections above and below section 17 will serve to effectively shield the seals formed by the portions of cement 21 above and below section 17 from the action of the explosive charge so that these seals will remain intact and elfectively segregate formation 11 from the intrusion of nudesired fluids, such as water, which may be present in the overor under'lying earth formations. Fig. 2 illustrates the parts of 'the apparatus after the walls of section 17 have been shattered and the pipe string opened to communication with earth formation 11.

Figs. 3 and 4 illustrate another apparatus embodiment in accordance with this invention. Instead of employing a pipe section 17 composed entirely of glass, as in the previously described embodiment, one of the metal pipe sections, designated by the numeral 25, is employed for positioning opposite the earth formation from which production is to'be obtained. Pipe section 25 will be connected to the adjacent pipe sections 15 in the usual manner by means of conventional threaded collars 26-426. The wall of section 25 will be provided with a plurality of elongated, angularly spaced, slots or windows 27, which will be initially closed by correspondingly shaped glass inserts 23 which may be held in place in windows 27 by any suitable and conventional fastening means, which may be any well-known cement suitable for forming a tight sealing bond between glass and metal such as steel.

This embodiment is employed in the same manner as the previously described embodiment, the pipe string being inserted 'in the well bore to position section 25 opposite earth formation 11 and then cemented in place in the usual manner. Thereafter an explosive charge, such as chargeg22, will be set off in the bore of section 25 to shatter glass inserts 28 and thereby open windows 27 to communication with formation 11. While the total area of windows 27 will necessarily be less than the area of the opening provided by the previously described embodiment, the combined area of windows 27 will be very large compared with existing devices and will usually correspond to a substantial portion of the area of the exposed face of formation 11.

The number and dimensions .of windows 27 will normally be selected to .provide the maximum area of open ing in the wall of section 25 while leaving enough intervening metal sections to retain a degree of over-all strength in section 25 sufiicient to permit it to perform its usual functions as a part of pipe string 14 during insertion in the well bore and in the cementing operations.

Fig. illustrates a modified form of relatively flexible connection means for connecting a glass pipe section, such as section 17, previously described, to a metal collar such as collars 16 or 26 above. In this modification a tubular sleeve 30, composed of relatively hard rubber or neoprene, has one end bonded directly to one end of glass section 17, as by means of a groove 31. The other end of sleeve 30 is provided with external threads 32 for threaded connection to the internal threads of collar 16. With this construction direct metal-to-glass contact is avoided while providing a relatively resilient connection between section 17 and collar 16 to absorb shock and bending stresses as previously described.

Fig. 6 illustrates another modification of the embodiment illustrated in Figs. 1 and 2. This modification is designed for use in cases where the producing formation 11 is of relatively large thickness. In such a case, it will usually be found preferable to make up section 17 from a number of relatively short pieces of glass tubing 35 coupled together by metal collars 36 which may be similar in form to collars 16 and 26 of the previously described embodiments and employing connection means between the glass sections and the collars similar to the above-described embodiments illustrated in Figs. 1 and 5. By employing short lengths of glass tubing, coupled together as described, the danger of breakage inherent in a single long piece of glass tubing will be obviated while providing in the pipe string a removable section having an over-all length corresponding to that of formation 11. Ordinarily, when the thickness of formation 11 exceeds, say, three feet, it will be found preferable to employ a plurality of short lengths of glass tubing.

It will be understood that all glass sections 17 may be interspersed with glass windowed steel sections like section 25 of Fig. 3. Also a series of the latter may be used instead of a single windowed section.

From the foregoing it will be seen that this invention provides methods and apparatus for completing a well by which drainage channels of large area may be formed to provide communication between a prospective producing formation and a pipe string extending into a well bore.

It will also be understood that other readily frangible or shatterable materials may be employed instead of glass for constructing section 17 and inserts 28. Such other materials include hard, brittle plastics, ceramic materials, cast metals such as cast iron, cast aluminium, cast magnesium and the like. In general, any material may be used which has substantial tensile and compressive strength but which will be relatively much more frangible than steel, whereby such material will be shattered preferentially with respect to adjacent steel portions by the action of moderate explosive changes.

It will be understood that numerous modifications and changes may be made in the method steps and in the details of the apparatus in accordance with this invention within the spirit of the invention but without departing from the scope of the appended claims.

What I claim and desire to secure by Letters Patent 15:

1. In well drilling wherein a bore hole is drilled through an earth formation containing fluid such as oil or gas, apparatus for completing the well for production of such fluid, comprising, a pipe string insertible in said well bore and extending through said formation, said pipe string being composed of a plurality of end-to-end threadedly connected tubular sections, at least one of said sections being composed entirely of glass adapted to be positioned opposite said formation, and resilient connector means for connecting said glass section to adjacent metal sections of said pipe string, said glass section having a length equal to a substantial portion of the length of said formation and being shatterable to thereby provide a correspondingly sized opening in the wall of said pipe string communicating with said formation.

2. Apparatus according to claim 1, wherein said means for connecting said glass section to adjacent metal sections includes a connector sleeve composed of resilient composition material connecting the ends of said glass section to adjacent metal sections.

3. Apparatus according to claim 1, wherein said means for connecting said glass section to adjacent metal sections includes a connector sleeve composed of resilient composition material having one end bonded directly to an end of said glass section and the other end threadedly connected to an adjacent metal section.

4. Apparatus according to claim 1, wherein said means for connecting said glass section to adjacent metal sections comprises external threads on the ends of said glass section, an internally threaded coupling on the end of an adjacent metal section for receiving the threaded end of said glass section, and a threaded bushing composed of resilient composition material interposed between the threads on the glass section and those in said coupling.

References Cited in the file of this patent UNITED STATES PATENTS 1,582,184 Mims Apr. 27, 1926 2,164,266 Armentrout et a1 June 27, 1939 2,173,033 Armentrout et al Sept. 12, 1939 2,219,022 Salnikov Oct. 22, 1940 2,414,349 Alexander Jan. 14, 1947 2,436,036 Defenbaugh Feb. 17, 1948 

